1. Field of the Invention
The present invention relates to a novel liquid crystal. The invention further relates to a novel liquid crystal display using the liquid crystals.
2. Description of the Related Art
When an electric field is applied, a ferroelectric liquid crystal exhibits a response speed which is several tens to several hundreds of times faster than that of the nematic liquid crystal that has heretofore been used in the liquid crystal displays, and is, therefore, drawing attention as a material of a new display system and its study has now been continued.
The ferroelectric liquid was discovered by Meyer of the U.S.A. in 1976. This system was obtained by introducing asymmetric carbon atoms into a compound that expresses smectic C to realize a chiral smectic C-phase, lowering the symmetry of the system and exhibiting ferroelectricity.
In 1996, Niori et al. have discovered a compound that exhibits ferroelectricity without introducing asymmetric carbon atoms into the system. From its molecular shape, this compound is called banana-type liquid crystal or bent-type liquid crystal, and is very advantageous in the cost of production as compared to the conventional ferroelectric liquid crystals since it does not require a step of chiral division which is necessary for the asymmetric carbon-introduced systems. The banana-type liquid crystal makes it possible to fabricate a ferroelectric liquid crystal display more economically than using the conventional ferroelectric liquid crystals.
The banana-type liquid crystals of new structures and compositions have been developed (see, for example, JP-A-9-221456 (patent document 1), JP-A-11-256163 (patent document 2) and JP-A-2002-161277 (patent document 3)). A report has also been made concerning the phase structure of the banana-type liquid crystals (see, for example, J. Watanabe, T. Izumi, T. Niori, M. Zennyoji, Y. Takanishi, H. Takezoe, Mol. Cryst. Liq. Cryst. 346, 77, 2000 (non-patent document 1)).
In the ferroelectric smectic liquid crystal phase formed by the conventional banana-type liquid crystals, however, the molecules have a tilted structure being tilted relative to the direction of normal to the smectic liquid crystal layer, involving a problem in that three liquid crystal phases of (+) chiral, (−) chiral and racemic are mixed together depending upon the manner of tilting.
In fabricating a liquid crystal display (LCD), it is an essential requirement to uniformly arrange the liquid crystal molecules in the cells. With the three kinds of liquid crystal phases being mixed together as described above, however, it is difficult to uniformly arrange the liquid crystal molecules in the cells.